html {
  width: 100%;
}
html body {
  width: 100%;
}
html body .index {
  max-width: 750px;
  min-width: 300px;
  width: 100%;
  margin: 0 auto;
  position: relative;
  overflow: hidden;
}
html body .index .btn {
  width: 92%;
  letter-spacing: 0.2em;
  padding-left: 2%;
  line-height: 2.5;
  margin: 0.3rem auto;
  font-size: 0.48rem;
  color: #fff;
  text-align: center;
  background-color: #009688;
  border-radius: 5px;
}
